Bone marrow activation in response to metabolic syndrome and early atherosclerosis.

AIMS: Experimental studies suggest that increased bone marrow (BM) activity is involved in the association between cardiovascular risk factors and inflammation in atherosclerosis. However, human data to support this association are sparse. The purpose was to study the association between cardiovascular risk factors, BM activation, and subclinical atherosclerosis. METHODS AND RESULTS: Whole body vascular 18F-fluorodeoxyglucose positron emission tomography/magnetic resonance imaging (18F-FDG PET/MRI) was performed in 745 apparently healthy individuals [median age 50.5 (46.8-53.6) years, 83.8% men] from the Progression of Early Subclinical Atherosclerosis (PESA) study. Bone marrow activation (defined as BM 18F-FDG uptake above the median maximal standardized uptake value) was assessed in the lumbar vertebrae (L3-L4). Systemic inflammation was indexed from circulating biomarkers. Early atherosclerosis was evaluated by arterial metabolic activity by 18F-FDG uptake in five vascular territories. Late atherosclerosis was evaluated by fully formed plaques on MRI. Subjects with BM activation were more frequently men (87.6 vs. 80.0%, P = 0.005) and more frequently had metabolic syndrome (MetS) (22.2 vs. 6.7%, P < 0.001). Bone marrow activation was significantly associated with all MetS components. Bone marrow activation was also associated with increased haematopoiesis-characterized by significantly elevated leucocyte (mainly neutrophil and monocytes) and erythrocyte counts-and with markers of systemic inflammation including high-sensitivity C-reactive protein, ferritin, fibrinogen, P-selectin, and vascular cell adhesion molecule-1. The associations between BM activation and MetS (and its components) and increased erythropoiesis were maintained in the subgroup of participants with no systemic inflammation. Bone marrow activation was significantly associated with high arterial metabolic activity (18F-FDG uptake). The co-occurrence of BM activation and arterial 18F-FDG uptake was associated with more advanced atherosclerosis (i.e. plaque presence and burden). CONCLUSION: In apparently healthy individuals, BM 18F-FDG uptake is associated with MetS and its components, even in the absence of systemic inflammation, and with elevated counts of circulating leucocytes. Bone marrow activation is associated with early atherosclerosis, characterized by high arterial metabolic activity. Bone marrow activation appears to be an early phenomenon in atherosclerosis development.[Progression of Early Subclinical Atherosclerosis (PESA); NCT01410318].

Coexistence of transmural and lateral wavefront progression of myocardial infarction in the human heart.

INTRODUCTION AND OBJECTIVES: According to the wavefront phenomenon described in the late 1970s, myocardial infarction triggered by acute coronary occlusion progresses with increasing duration of ischemia as a transmural wavefront from the subendocardium toward the subepicardium. However, whether wavefront progression of necrosis also occurs laterally has been disputed. We aimed to assess the transmural and lateral spread of myocardial damage after acute myocardial infarction in humans and to evaluate the impact of metoprolol on these. METHODS: We assessed myocardial infarction in the transmural and lateral dimensions in a cohort of 220 acute ST-segment elevation myocardial infarction (STEMI) patients from the METOCARD-CNIC trial (Effect of Metoprolol in Cardioprotection During an Acute Myocardial Infarction). The patients underwent cardiac magnetic resonance imaging at 5 to 7 days and 6 months post-STEMI. RESULTS: On day 5 to 7 post-STEMI cardiac magnetic resonance, there was a strong linear correlation between the transmural and lateral extent of infarction (delayed gadolinium enhancement) (r=-0.88; P<.001). Six months after STEMI, myocardial scarring (delayed gadolinium enhancement) was significantly less extensive in the transmural and lateral dimensions, suggesting that infarct resorption occurs in both. Furthermore, progression in both directions occurred both in patients receiving metoprolol and control patients, implying that myocardial salvage occurs both in the transmural and the lateral direction. CONCLUSIONS: Our findings challenge the assumption that irreversible injury does not spread laterally. A "circumferential" or multidirectional wavefront would imply that cardioprotective therapies might produce meaningful salvage at lateral borders of the infarct. This trial was registered at ClinicalTrial.gov (Identifier: NCT01311700).

Metoprolol blunts the time-dependent progression of infarct size.

Early metoprolol administration protects against myocardial ischemia-reperfusion injury, but its effect on infarct size progression (ischemic injury) is unknown. Eight groups of pigs (total n = 122) underwent coronary artery occlusion of varying duration (20, 25, 30, 35, 40, 45, 50, or 60 min) followed by reperfusion. In each group, pigs were randomized to i.v. metoprolol (0.75 mg/kg) or vehicle (saline) 20 min after ischemia onset. The primary outcome measure was infarct size (IS) on day7 cardiac magnetic resonance (CMR) normalized to area at risk (AAR, measured by perfusion computed tomography [CT] during ischemia). Metoprolol treatment reduced overall mortality (10% vs 26%, p = 0.03) and the incidence and number of primary ventricular fibrillations during infarct induction. In controls, IS after 20-min ischemia was ≈ 5% of the area AAR. Thereafter, IS progressed exponentially, occupying almost all the AAR after 35 min of ischemia. Metoprolol injection significantly reduced the slope of IS progression (p = 0.004 for final IS). Head-to-head comparison (metoprolol treated vs vehicle treated) showed statistically significant reductions in IS at 30, 35, 40, and 50-min reperfusion. At 60-min reperfusion, IS was 100% of AAR in both groups. Despite more prolonged ischemia, metoprolol-treated pigs reperfused at 50 min had smaller infarcts than control pigs undergoing ischemia for 40 or 45 min and similar-sized infarcts to those undergoing 35-min ischemia. Day-45 LVEF was higher in metoprolol-treated vs vehicle-treated pigs (41.6% vs 36.5%, p = 0.008). In summary, metoprolol administration early during ischemia attenuates IS progression and reduces the incidence of primary ventricular fibrillation. These data identify metoprolol as an intervention ideally suited to the treatment of STEMI patients identified early in the course of infarction and requiring long transport times before primary angioplasty.

R2 prime (R2') magnetic resonance imaging for post-myocardial infarction intramyocardial haemorrhage quantification.

AIMS: To assess whether R2* is more accurate than T2* for the detection of intramyocardial haemorrhage (IMH) and to evaluate whether T2' (or R2') is less affected by oedema than T2* (R2*), and thus more suitable for the accurate identification of post-myocardial infarction (MI) IMH. METHODS AND RESULTS: Reperfused anterior MI was performed in 20 pigs, which were sacrificed at 120 min, 24 h, 4 days, and 7 days. At each time point, cardiac magnetic resonance (CMR) T2- and T2*-mapping scans were recorded, and myocardial tissue samples were collected to quantify IMH and myocardial water content. After normalization by the number of red blood cells in remote tissue, histological IMH increased 5.2-fold, 10.7-fold, and 4.1-fold at Days 1, 4, and 7, respectively. The presence of IMH was correlated more strongly with R2* (r = 0.69; P = 0.013) than with T2* (r = -0.50; P = 0.085). The correlation with IMH was even stronger for R2' (r = 0.72; P = 0.008). For myocardial oedema, the correlation was stronger for R2* (r = -0.63; P = 0.029) than for R2' (r = -0.50; P = 0.100). Multivariate linear regressions confirmed that R2* values were significantly explained by both IMH and oedema, whereas R2' values were mostly explained by histological IMH (P = 0.024) and were little influenced by myocardial oedema (P = 0.262). CONCLUSION: Using CMR mapping with histological validation in a pig model of reperfused MI, R2'more accurately detected IMH and was less influenced by oedema than R2* (and T2*). Further studies are needed to elucidate whether R2' is also better suited for the characterization of post-MI IMH in the clinical setting.

Editor's Choice- Pathophysiology and therapy of myocardial ischaemia/reperfusion syndrome.

There is a need to find interventions able to reduce the extent of injury in reperfused ST-segment elevation myocardial infarction (STEMI) beyond timely reperfusion. In this review, we summarise the clinical impact of STEMI from epidemiological, clinical and biological perspectives. We also revise the pathophysiology underlying the ischaemia/reperfusion syndrome occurring in reperfused STEMI, including the several players involved in this syndrome, such as cardiomyocytes, microcirculation and circulating cells. Interventions aimed to reduce the resultant infarct size, known as cardioprotective therapies, are extensively discussed, putting the focus on both mechanical interventions (i.e. ischaemic conditioning) and promising pharmacological therapies, such as early intravenous metoprolol, exenatide and other glucose modulators, N-acetylcysteine as well as on some other classic therapies which have failed to be translated to the clinical arena. Novel targets for evolving therapeutic interventions to ameliorate ischaemia/reperfusion injury are also discussed. Finally, we highlight the necessity to improve the study design of future randomised clinical trials in the field, as well as to select patients better who can most likely benefit from cardioprotective interventions.

The microRNA-29/PGC1α regulatory axis is critical for metabolic control of cardiac function.

Different microRNAs (miRNAs), including miR-29 family, may play a role in the development of heart failure (HF), but the underlying molecular mechanisms in HF pathogenesis remain unclear. We aimed at characterizing mice deficient in miR-29 in order to address the functional relevance of this family of miRNAs in the cardiovascular system and its contribution to heart disease. In this work, we show that mice deficient in miR-29a/b1 develop vascular remodeling and systemic hypertension, as well as HF with preserved ejection fraction (HFpEF) characterized by myocardial fibrosis, diastolic dysfunction, and pulmonary congestion, and die prematurely. We also found evidence that the absence of miR-29 triggers the up-regulation of its target, the master metabolic regulator PGC1α, which in turn generates profound alterations in mitochondrial biogenesis, leading to a pathological accumulation of small mitochondria in mutant animals that contribute to cardiac disease. Notably, we demonstrate that systemic hypertension and HFpEF caused by miR-29 deficiency can be rescued by PGC1α haploinsufficiency, which reduces cardiac mitochondrial accumulation and extends longevity of miR-29-mutant mice. In addition, PGC1α is overexpressed in hearts from patients with HF. Collectively, our findings demonstrate the in vivo role of miR-29 in cardiovascular homeostasis and unveil a novel miR-29/PGC1α regulatory circuitry of functional relevance for cell metabolism under normal and pathological conditions.

Mirabegron, a Clinically Approved ß3 Adrenergic Receptor Agonist, Does Not Reduce Infarct Size in a Swine Model of Reperfused Myocardial Infarction.

The administration of the selective ß3 adrenergic receptor (ß3AR) agonist BRL-37344 protects from myocardial ischemia/reperfusion injury (IRI), although the lack of clinical approval limits its translatability. We tested the cardioprotective effect of mirabegron, the first-in-class ß3AR agonist approved for human use. A dose-response study was conducted in 6 pigs to select the highest intravenous dose of mirabegron without significant detrimental hemodynamic effect. Subsequently, closed chest anterior myocardial infarction (45 min ischemia followed by reperfusion) was performed in 26 pigs which randomly received either mirabegron (10 µg/kg) or placebo 5 min before reperfusion. Day-7 cardiac magnetic resonance (CMR) showed no differences in infarct size (35.0 ± 2.0% of left ventricle (LV) vs. 35.9 ± 2.4% in mirabegron and placebo respectively, p = 0.782) or LV ejection fraction (36.3 ± 1.1 vs. 34.6 ± 1.9%, p = 0.430). Consistent results were obtained on day-45 CMR. In conclusion, the intravenous administration of the clinically available selective ß3AR agonist mirabegron does not reduce infarct size in a swine model of IRI.

Safety and efficacy of in-hospital clopidogrel-to-prasugrel switching in patients with acute coronary syndrome. An analysis from the 'real world'.

Antiplatelet switching in the management of acute coronary syndrome (ACS) seems to be safe, but prospective data are limited. This retrospective study assessed the safety and efficacy of in-hospital clopidogrel-to-prasugrel switching in patients with ACS. We analysed 525 consecutive patients with ACS admitted to our coronary care unit. We assessed the prevalence and the short-term outcomes of in-hospital clopidogrel-to-prasugrel switching. Bleeding and thrombotic events were assessed using propensity score matching analysis. A total of 468 patients received acetylsalicylic acid and a P2Y12 ADP receptor inhibitor. Medication switching occurred in 117 patients (25 %). Compared with the clopidogrel group, the switching group consisted preferentially of younger males with STEMI, exhibited fewer comorbidities, and had lower ischaemic risk. We found no differences between the switching group and the clopidogrel group in the bleeding rate [3.6 vs. 2.3 %, odds ratio (OR):1.59 95 % confidence interval (CI): 0.26-9.7, p NS], and in adverse cardiac or cerebrovascular events (MACCE) (5 vs. 8.4 %, OR: 0.57 95 % CI 0.16-2, p NS). In-hospital switching from clopidogrel to prasugrel in a selected high-risk ACS population resulted in a similar incidence of in-hospital haemorrhagic and thrombotic events. This strategy should be clarified in further randomised studies.